Conserving plants is one of the most significant challenges of our time—and a major focus at the Chicago Botanic Garden. From studying soil to banking seeds, from restoring habitats and protecting endangered plant species to developing new ones, Garden scientists are fighting plant extinction, pollution, and climate change through diverse and exciting research.
Most plants hate saltwater. Pour saltwater on your houseplants and, a little while later, you’ll have some wilty plants. But mangroves can grow—and thrive—in saltwater.
You may have seen mangroves if you’ve been to the Florida Everglades or gone to an island in the Caribbean. Mangroves are trees that live in tropical, coastal zones and have special adaptations for life in saltwater. One of these adaptations is in how they reproduce: mangroves don’t make seeds. Instead, they make living, buoyant embryos called propagules (prop-a-gyule).
Mangrove propagules come in different shapes and sizes. Each species has its own unique propagule.
Mangroves produce a huge number of propagules the same way an oak would make hundreds of acorns.
These relatively small propagules could become giant red mangrove trees.
Black mangrove propagules on a branch; their outer coating will dissolve on their journey downstream.
Propagules come in different shapes and sizes. These are from a tea mangrove (Pelliciera rhizophorae) tree.
Normally, trees reproduce with seeds. You’ve probably seen the whirlybirds of maples and acorns of oaks. These seeds can go dormant. They are basically “asleep” or hibernate until something—water, temperature, or physical damage—wakes them up, allowing them to start growing months or years after they are produced.
Here I am with a couple of mangrove specimens. These roots are in water at high tide, but exposed at low tide.
Propagules, on the other hand, don’t have that luxury—they fall off their parent tree, ready to start rooting and growing a new tree. Nature has provided an amazing way for the mangrove seeds to move away from the parent tree: they float.
As the propagules float through the water, they shed their outermost layer and immediately start growing roots. The clock starts ticking as soon the propagules fall—if they don’t find a suitable place to start growing within a certain amount of time, they die. If a mangrove propagule ends its journey at a location that’s suitable for growth, the already-rooting propagule will send up its first set of leaves—cotyledons.
Ocean currents can take propagules thousands of miles away from where they started. A mangrove’s parent tree might be around the corner or around the continent.
Dr. Emily Dangremond is a postdoctoral researcher at the Smithsonian Environmental Research Center and a visiting scientist at the Chicago Botanic Garden. She is currently studying the ecological and evolutionary consequences of mangroves responding to climate change at their northernmost limit in Florida.
Students in the Chicago Botanic Garden and Northwestern University Program in Plant Biology and Conservation were given a challenge: Write a short, clear explanation of a scientific concept that can be easily understood by non-scientists. This post is part of their series.
When buckthorn moves in to the ecosystem, it dominates.
Imagine a friend invites you to a dinner party, promising a delicious spread of food and libations. You arrive, excited and hungry, only to find nothing but raw kale, brought by an uninvited guest. Regardless of your feelings about kale, this would be pretty underwhelming. The other guests are obviously disappointed about the monotonous spread. Most people leave, and because most people aren’t eating the kale, the kale continues to dominate the party. Even if someone brought in better foods that more people enjoy, there is no room on the tables. The kale is everywhere!
Common buckthorn (Rhamnus cathartica)
While not a perfect analogy, this anecdote relays the reasons why buckthorn invasion is detrimental to forest ecosystems. The dinner guests are like the other plants and animals that usually live in the woods. They have certain dietary needs, and if those needs cannot be met, they will have to leave and find another place to live. The more one species dominates (kale, or in many local forests, buckthorn) the fewer species can live there, leading to the ecological equivalent of a party that ends at 8:30, just as everyone was arriving. While it may be true that one person at the party really likes kale, it’s hardly fair for the preferences of that person to supersede everyone else’s needs. In the case of buckthorn, many have opposed its removal because that denies robins a berry that they enjoy. However, keeping the buckthorn (which doesn’t belong there in the first place) is like keeping all of the kale on the tables and not allowing for other foods to be served just for that one person. Even more frustrating, the person that likes kale has plenty of other dietary options. Kale isn’t even their favorite food!
The McDonald woods shows healthy filtered sunlight and native plant understory growth after buckthorn removal.
To many people, the idea of cutting down trees to help forests grow stronger is counterintuitive. But buckthorn is no ordinary tree. It is an invasive species, meaning that it doesn’t belong in Chicago area forests, and it steals resources from the plants that are supposed to live here. So remember, when you hear people talking about cutting down buckthorn, they are actually doing it to make the habitat healthier and more inclusive in the long term. They are working to replace the kale at the party with better food and drinks, ensuring that all the guests that were invited can have a good time, staying up until sunrise.
Bob Sherman is an undergraduate studying environmental science at Northwestern University. His research interests include prairie restoration and how abiotic factors impact prairie and forest ecosystems. He hopes that his research will have a positive impact on ecosystem restoration and management.
Students in the Chicago Botanic Garden and Northwestern University Program in Plant Biology and Conservation were given a challenge: Write a short, clear explanation of a scientific concept that can be easily understood by non-scientists. This post is part of their series.
For more than two decades, leaders in conservation science have come to the Chicago Botanic Garden each summer to discuss timely topics from monarch butterflies to assisted plant migration.
Butterfly on Liatris
Seeds will be planted again on Monday, June 13, when regional stewardship professionals, academics, restoration volunteers, and interns gather for the Janet Meakin Poor Research Symposium. The annual day of lectures and discussions covers the latest findings in conservation research and best practices in restoration, while inspiring conversations and new partnerships.
“I think the science that pertains to land management is always evolving, and therefore best practices are always evolving,” said Kay Havens, Ph.D., Medard and Elizabeth Welch senior director, Ecology and Conservation, and the moderator of the symposium.
The 2015 symposium focused on restoration solutions for large-scale implementation, and this year’s theme, Seed Sourcing for Restoration in a Changing Climate, builds on the concept of seed management. “It focuses on conservation research and restoration and tries to make links with the land management community—so not just reporting the science but also reporting how that could influence land management,” explained Dr. Havens. This subject is especially timely, according to Havens, as it follows the first year of the National Seed Strategy for Rehabilitation and Restoration. The Garden has played a key role in establishing the seed strategy, which will create a network to ensure native seeds are available in restoration efforts, especially in fire-ravaged western rangelands.
The Dixon Prairie in July
“I think the need for restoration increases annually,” said Havens. “We are facing a more and more degraded planet every year, and as the climate changes and natural disasters like hurricanes and floods increase, the need for restoration increases.”
Rick Overson is fascinated with insects—especially the kinds that love desert climates like in Arizona, where he grew up and earned his Ph.D. in biology. After completing a postdoctoral assignment in northern California, he decided it was time to get to know the little buggers even better, so Dr. Overson hopped on a plane for Chicago and stepped out into the subzero temperatures of the polar vortex to do just that.
Dr. Rick Overson with hawkmoth specimens
The devoted entomologist didn’t expect to see the insects in Chicago, but he was eager to join research at the Chicago Botanic Garden. A multidisciplinary team was assembling there to look for scent variations within Onagraceae, the evening primrose family, and connections from floral scent to insect pollinators and predators. The findings could answer questions about the ecology and evolution of all insects and plants involved. Overson is a postdoctoral researcher for the initiative, along with Tania Jogesh, Ph.D.
“Landscapes of Linalool: Scent-Mediated Diversification of Flowers and Moths across Western North America” is funded by a $1.54 million Dimensions in Biodiversity grant from the National Science Foundation. The project is headed by Garden scientists Krissa Skogen, Ph.D.,Norman Wickett, Ph.D., and Jeremie Fant, Ph.D. It was developed from prior research conducted by Dr. Skogen on scent variation among Oenothera harringtonii plants in southern Colorado.
“For me, the most important thing coming out of this project is documenting and showing this incredible diversity that happens inside a species,” said Overson. “It’s vitally important for me to break down this idea of a species as a discrete unit. It’s a dynamic thing that is different in one place than another. That factors into conservation and our understanding of evolution.” In this case, he and his colleagues theorize that the evolution of the insect pollinators and predators is connected to the evolution of the scent of the plants.
Evening primrose in bloom on the plains of New Mexico. Photo by Dr. Rick Overson
The first two years of field work brought Overson back to his desert home. He traveled across Arizona, Utah, and nearby states with a group of about five scientists during summer months when the flowers were blooming. The team visited several populations each of 16 species of flower for a total of 60 locations. Overson and the team identified and documented the insects visiting the plants and compiled scent chemistry from the flowers. Their tool kit included a pump to pull the scent from a flower onto tiny polymer beads that held the scent inside of a vial. From there, they extracted the scent chemicals at the end of the research day or night. “It’s definitely the case that this pattern of scent variation inside a species is very common in this group,” he said of the team’s preliminary findings.
A beneficial pollinator, the hawkmoth, visits an evening primrose (Oenothera harringtonii).
In the field they also took video recordings of pollinator behavior to see who visited which flowers and when. The pollinators, including hawkmoths and bees, follow scents to find various rewards such as pollen or nectar. The insects are selective, and make unique choices on which plants to visit.
Why do specific pollinators visit specific plants? In this case, the Skogen Lab is finding that it is in response to the scent, or chemical communication, each flower releases. “In the natural world those [scents] are signals, they are messages. Those different compounds that flowers are producing, a lot of them are cocktails of different types of chemicals. They could be saying very different things.”
Nature is complicated. Here, a wasp lays eggs through a flower bud into a hidden Mompha moth inside. Its larvae will eventually destroy both the moth and the flower. Photo by Dr. Rick Overson
A destructive micromoth called a microlepidopteran (classified in the genus Mompha), has also likely learned how to read the scent messages of its hosts. The specialist herbivore lays eggs on plants leading to detrimental effects for seed production. The team’s field work has shown that Mompha moths only infect some populations of flowers. When and why did the flowers evolve to deter or attract all of these different pollinators? Or was it the pollinators who drove change?
At the Garden, Overson is currently focused on exploring the genomes, or DNA set, of these plants to create a phylogeny, which looks like a flow chart and reads like a story of evolution. “Right now we don’t know how all of these species are interrelated,” he explained. When the phylogeny is complete, they will have a more comprehensive outline of key relationships and timing than ever before. That information will allow scientists to determine where specific scents and other traits originated and spread. He will explore the evolution of important plant traits using the phylogeny including the color of the flowers and their pollinators, to answer as many questions as possible about relationships and linked evolutionary events.
In addition, the team is looking at population genetics so they can determine the amount of breeding occurring between plant locations by either seed movement or by pollinators. They will also look for obstacles to breeding, such as interference by mountain ranges or cities.
“Relationships among flowering plants and insects represent one of the great engines of terrestrial diversity,” wrote principal investigator Krissa Skogen, PhD, in ablog post announcing the grant.
The way that genes have flowed through different populations, or have been blocked from doing so over time, can also lead to changes in a species that are significant enough to drive speciation, or the development of new species, said Overson. “The big idea is that maybe these patterns that are driving diversity within these flowers could ultimately be leading to speciation.”
By understanding these differences and patterns, the scientists may influence conservation decisions, such as what locations are most in need of protection, and what corridors of gene flow are most important to safeguard.
Dr. Rick Overson in the field
“We absolutely can’t live without plants or insects, it’s impossible,” remarked Overson. “Plants and insects are dominant forces in our terrestrial existence. Very few people would argue that we haven’t heavily modified the landscape where these plants and insects live. I think it is crucially important to understand these interactions for the sake of the natural world, agriculture and beyond.”
When Dr. Overson is taking a break from the laboratory, he visits the Desert Greenhouse in the Regenstein Center, which feels like home to him.
Be the first to grow these ten new plants—including Lunar Eclipse false indigo—just patented via the Chicagoland Grows, Inc. plant introduction program and on sale for the first time.
Look for them at Chicago-area garden centers, said Jim Ault, Ph.D., who manages the program for the Chicago Botanic Garden. He’s proud of all of them, but two are special, said Ault, the Gaylord and Dorothy Donnelley Director of Ornamental Plant Research: Baptisia ‘Lunar Eclipse’, for its flowers that change from creamy white to deep violet as the plant ages, and Baptisia ‘Sunny Morning’, for its profusion of yellow flowers on dark charcoal stems.
Blue Mound false indigo Baptisia australis ‘Blue Mound’
Lavender Rose false indigo Baptisia ‘Lavender Rose’
Dr. Emily Dangremond is a postdoctoral researcher at the Smithsonian Environmental Research Center and a visiting scientist at the Chicago Botanic Garden. She is currently studying the ecological and evolutionary consequences of mangroves responding to climate change at their northernmost limit in Florida. 
